Flow sensor with bypass taps in laminar flow element laminarizing channel

ABSTRACT

A flow sensor includes a main flow body, a laminar flow element, a first bypass tap, and a second flow element sensor tap. The main flow body has a first main flow port, a second main flow port, a main flow channel, a first bypass tap, a second bypass tap, and a bypass flow channel. The laminar flow element is disposed within the main flow channel. The bypass flow channel has a cross sectional area, and the first bypass tap and the second bypass tap each have a cross sectional area that is greater than the maximum cross sectional area of the bypass flow channel.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/549,628, filed Oct. 20, 2011.

TECHNICAL FIELD

The present invention generally relates to flow sensors, and moreparticularly relates to a flow sensor with a laminar flow element andbypass taps within a channel of the laminar flow element, and one ormore flow restrictors in the bypass channel.

BACKGROUND

High flow sensors generally use a bypass flow channel in combinationwith a main flow channel. A laminar flow element (LFE) may beincorporated in the main flow channel. A typical LFE may includemultiple parallel flow channels with relatively small cross-sectionalarea to laminarize the main flow and create a pressure restriction. Thebypass flow channel is fluidly communicated to the main flow channel viataps that are disposed perpendicular to the main flow channel. The tapsmay include a first tap and a second tap, with the first tap disposedupstream of the LFE and the second tap disposed downstream of the LFE.

The perpendicular orientation of the taps presents static pressure atthe taps. The difference in the static pressure between the first andsecond taps drives flow through the bypass flow channel. The flowratethrough the bypass flow channel may be controlled by features of thebypass, such as length and diameter, or an orifice or tube shapedfeature may be used to limit bypass flow rate.

Disposing the taps upstream and downstream of the LFE places the tapswhere a large flow volume is available for redirection into the bypassflow channel. However, this arrangement can exhibit certain drawbacks.First, with this arrangement the taps are placed in a more turbulent,large diameter flow zone, and flow agitation from turbulence increasessignal noise. Second, the flow passing through the geometry changes atthe inlet and outlet of the LFE can create unstable flow and pressurechanges at the taps, which can adversely affect sensor signal. Third,non-linear orifice effects that are inherent in restricting flow throughthe bypass can create non-linear output and a reduction in signal inlower flow ranges.

Hence, there is a need for a flow sensor that addresses the above-noteddrawbacks, and/or creates a bypass flow rate with minimal components andsize, and/or implements a relatively long bypass flow channel to reduceorifice effects caused by differences in relationship of cross-sectionalarea of the bypass channel to the partitions in the LFE. The presentinvention addresses at least these needs.

BRIEF SUMMARY

In one embodiment, a flow sensor includes a main flow body, a laminarflow element, a bypass element, a first bypass tap, and a second bypasstap. The main flow body has a first main flow port, a second main flowport, and a main flow channel between the first main flow port and thesecond main flow port. The laminar flow element is disposed within themain flow channel between the first main flow port and the second mainflow port and has a first end, a second end, and an outer surface. Thefirst end faces the first main flow port, and the second end faces thesecond main flow port. The bypass element is disposed adjacent to themain flow body and includes a bypass flow channel. The first bypass tapextends through the outer surface of the laminar flow element and isdisposed between the first end and the second end of the laminar flowelement. The first bypass tap fluidly communicates the main flow channelwith the bypass flow channel. The second bypass tap extends through theouter surface of the laminar flow element and is disposed between thefirst end and the second end of the laminar flow element. The secondbypass tap fluidly communicates the main flow channel with the bypassflow channel. The bypass flow channel has a cross sectional area, andthe first bypass tap and the second bypass tap each have a crosssectional area that is greater than the cross sectional area of thebypass flow channel.

In another embodiment, a flow sensor includes a main flow body, alaminar flow element, and a flow sensor. The main flow body has a firstmain flow port, a second main flow port, a main flow channel between thefirst main flow port and the second main flow ports, a first bypass tap,a second bypass tap, and a bypass flow channel. The laminar flow elementis disposed within the main flow channel between the first main flowport and the second main flow port and has a first end and a second end.The first end faces the first main flow port, and the second end facesthe second main flow port. The flow sensor is coupled to the main flowbody and is disposed within the bypass flow channel. The flow sensor isconfigured to sense fluid flow through the bypass flow channel. Thefirst bypass tap is disposed between the first end and the second end ofthe laminar flow element, and fluidly communicates the main flow channelwith the bypass flow channel. The second bypass tap is disposed betweenthe first end and the second end of the laminar flow element, andfluidly communicates the main flow channel with the bypass flow channel.The bypass flow channel has a cross sectional area, and the first bypasstap and the second bypass tap each have a cross sectional area that isgreater than the cross sectional area of the bypass flow channel.

In yet another embodiment, a flow sensor includes a main flow body, alaminar flow element, and a bypass element. The main flow body has afirst main flow port, a second main flow port, a main flow channelbetween the first main flow port and the second main flow port, a firstbypass tap, and a second bypass tap. The laminar flow element isdisposed within the main flow channel between the first main flow portand the second main flow port and has a first end, a second end, and anouter surface. The first end faces the first main flow port, and thesecond end faces the second main flow port. The bypass element isdisposed adjacent to the main flow body and has a bypass flow channel.The first bypass tap is disposed between the first end and the secondend of the laminar flow element, and fluidly communicates the main flowchannel with the bypass flow channel. The second bypass tap is disposedbetween the first end and the second end of the laminar flow element,and fluidly communicates the main flow channel with the bypass flowchannel. The main flow channel is oriented about an axis that extendsbetween the first main flow port and the second main flow port. Thefirst bypass tap and the second bypass tap each have a width in adirection parallel to the axis and a length in a direction perpendicularto the width. The width is less than the length, and the first bypasstap and the second bypass tap each have a cross sectional area that isgreater than the cross sectional area of the bypass flow channel.

Furthermore, other desirable features and characteristics of the flowsensor will become apparent from the subsequent detailed description andthe appended claims, taken in conjunction with the accompanying drawingsand the preceding background.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will hereinafter be described in conjunction with thefollowing drawing figures, wherein like numerals denote like elements,and wherein:

FIGS. 1-4 each depict a simplified cross-section view of an embodimentof a flow sensor according to an exemplary embodiment;

FIG. 5 depicts a plan view of one embodiment of a laminar flow elementthat may be used to implement the flow sensors of FIGS. 1-4;

FIGS. 6 and 7 depict plan views of another embodiment of a laminar flowelement that may be used to implement the flow sensor of FIGS. 1-4;

FIG. 8 depicts a partial cross section view of the flow sensor of FIG.4, taken along line 8-8 in FIG. 1;

FIGS. 9 and 10 depict plan views of another embodiment of a laminar flowelement that may be used to implement the flow sensor of FIGS. 1-4;

FIGS. 11-14 depict plan views of yet another embodiment of a laminarflow element that may be used to implement the flow sensor of FIGS. 1-4;

FIGS. 15 and 16 depict plan views of still another embodiment of alaminar flow element that may be used to implement the flow sensor ofFIGS. 1-4; and

FIG. 17 depicts a simplified cross section view of a portion of anotherembodiment of a flow sensor.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. As used herein, the word “exemplary” means “serving as anexample, instance, or illustration.” Thus, any embodiment describedherein as “exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments. All of the embodiments describedherein are exemplary embodiments provided to enable persons skilled inthe art to make or use the invention and not to limit the scope of theinvention which is defined by the claims. Furthermore, there is nointention to be bound by any expressed or implied theory presented inthe preceding technical field, background, brief summary, or thefollowing detailed description.

A simplified cross section view of various embodiments of flow sensor100 that may be used to measure the rate of flow of a fluid is depictedin FIGS. 1-4, and includes a main flow body 102, a bypass element 104,and a laminar flow element (LFE) 106. Before describing the flow sensor100 in more detail, it is noted that the flow sensor 100 may be used inany one of numerous systems in which flow rate measurement is desired.Some non-limiting examples include ventilators and respirators.

The main flow body 102, which may be implemented using an integratedstructure or a plurality of components, includes an inner surface 108that defines a main flow channel 112, having a first main flow port 114and a second main flow port 116. Depending upon how the flow sensor 100is implemented, fluid may flow into the first main flow port 114,through the main flow channel 112, and out the second main flow port116. Alternatively, fluid may flow into the second main flow port 116,through the main flow channel 112, and out the first main flow port 114.In either case, the main flow channel 112 preferably has across-sectional shape and size compatible with any one of numerous flowsystems. The main flow body 102 additionally includes a first bypass tap122 and a second bypass tap 124, both of which are in fluidcommunication with the main flow channel 112 and are preferablyconfigured perpendicular to the axis 110.

The bypass element 104 is disposed adjacent to the main flow body 102and has a bypass flow channel 118 in fluid communication with the firstand second bypass taps 122, 124. Thus, a portion of the fluid flowingthrough the main flow channel 112 enters the bypass flow channel 118. Asmay be appreciated, the fluid flow rate in the bypass flow channel 118is typically a fraction of the fluid flow rate in the main flow channel112. Although the depicted flow sensor 100 includes two bypass taps 122,124, it will be appreciated that the flow sensor 100 could beimplemented with other numbers of bypass taps. It will additionally beappreciated that other methods of communicating flow from the main flowchannel 112 to bypass flow channel 118 may be used. Moreover, the bypasselement 104 may be formed integrally with the main flow body 102, asdepicted in FIG. 1, it may be formed separate from the main flow body102 and coupled thereto, as depicted in FIGS. 3 and 4, or it may be acombination of integral and separate components, as depicted in FIG. 2.

As FIGS. 1-4 further depict, a flow sensor 105 is coupled to the bypasselement 104, and is disposed in the bypass flow channel 118. The flowsensor 105 may be variously implemented, but in the depicted embodimentit is implemented using a micro-bridge sensor. The flow sensor 105 maybe variously coupled to the bypass element 104. For example, as depictedin FIGS. 1, 2 and 4, the flow sensor 105 may be coupled to or otherwisemounted on a circuit board or plate 107 that is subsequently coupled tothe bypass element 104. Alternatively, the flow sensor 105 may becoupled to or otherwise mounted on a circuit board or plate 107 that iscoupled to a separate portion 109 that is separately coupled to theremainder of the bypass element 104. During operation, as fluid flowsthrough the main flow channel 112, in either the first direction 126 orthe second direction 128, a portion of the fluid flows into and throughthe bypass flow channel 118. The flow sensor 105 thus measures the flowrate of fluid in the main flow channel 112 indirectly by measuring afraction of fluid flow through the bypass flow channel 118.

The LFE 106 is disposed in the main flow channel 112 and includes afirst end 132 and a second end 134. As is generally known, the LFE 106causes a pressure differential between the first and second main flowbody sensor taps 122, 124, which thereby facilitates fluid flow into thebypass flow channel 118. As is also generally known, the pressuredifferential is dependent on the geometry of the LFE 106, and increaseswith flow rate. Furthermore, the fluid flowing in the main flow channel112 will be increasingly turbulent as the flow rate increases. Thus, theLFE 106, in addition to creating the differential pressure, straightensand laminarizes the fluid flow in the main flow channel 112, therebyreducing turbulence. The LFE 106 reduces turbulence by forcing the fluidto flow through a plurality of flow channels 136. The pressure dropacross the LFE 106 may also be dependent on the size and uniformity ofthese flow channels 136. Preferably, the flow channels 136 are parallel,and may be circular ring shaped, grid shaped, honeycomb shaped, or roundtube shaped. It will be appreciated that the LFE 106 may be integratedinto a molded housing, or it may be a separate component such as ahoneycomb or molded part.

To further straighten and control the fluid flow in the main flowchannel 112, the flow sensor 100 may additionally include one or morescreens 138 on either or both sides of the LFE 106. In the depictedembodiment, the flow sensor 100 includes two screens—a first screen138-1 and a second screen 138-2. It will be appreciated, however, thatin other embodiments the flow sensor 100 may include more or less thanthis number of screens 138, if needed or desire.

As FIGS. 3 and 4 further depict, in some embodiments the LFE 106includes the first and second bypass taps 122, 124. As will be describedin more detail further below, in these embodiments the first and secondbypass taps 122, 124 extend through an outer surface of the LFE 106, andfluidly communicate the bypass flow channel 118 with the laminarizingzone of the LFE 106 between the first end 132 and the second end 134,respectively, of the LFE 106. In these embodiments, the first bypass tap122 is disposed closer to the first end 132 of the LFE 106, and thesecond bypass tap 124 is disposed closer to the second end 134 of theLFE 106. Disposing the first and second bypass taps 122, 124 at theselocations ensures that the taps 122, 124 are exposed to a relativelylower Reynolds number, and thus to more laminar flow. This dispositionadditionally assists in noise reduction in the signal output and reducespneumatic nonlinear orifice effects that may be created by the inlet andoutlet geometry inherent in an LFE 106. Also, the shorter distancebetween the bypass taps 122, 124, as compared to conventional bypass taplocations, reduces the differential pressure between these bypass taps122, 124 due to the shorter distance and by eliminating pressure lossesat the ends of the LFE 106. This can be advantageous for highsensitivity, fast response time sensors, such as a micro-bridge typesensor.

As FIGS. 3 and 4 also depict, in some embodiments the main flow body 102may include a first bypass flow port 123 and a second bypass flow port123. In these embodiments, the first bypass flow port 123 fluidlycommunicates the first bypass tap 122 with the bypass flow channel 118,and the second bypass flow port 125 fluidly communicates the secondbypass tap 124 with the bypass flow channel 118.

As illustrated in the embodiments depicted in FIGS. 1-4, one or moreflow restrictors 142 (two depicted) may be disposed in the bypass flowchannel 118 or, as depicted in phantom, some embodiments may beimplemented without the flow restrictor(s) 142. The flow restrictor(s)142, if included, limit(s) fluid flow into the bypass flow channel 118to an acceptable sensing range and may be variously implemented. Forexample, each flow restrictor 142 may be implemented as a long narrowlyshaped tube or as an orifice. No matter the specific implementation, theflow restrictor(s) 142 may be disposed upstream of the flow sensor 105,downstream of the flow sensor 105, or both.

Referring now to FIG. 5, one embodiment of the LFE 106 is depicted. Inthis embodiment, the areas of the first and second bypass taps 122, 124are enlarged to reduce the flow velocity presented to the bypass flowchannel 118. More specifically, the first and second bypass taps 122,124 each have a cross sectional area that is greater than the typicalcross sectional area of the bypass flow channel 118. As depicted moreclearly in FIG. 8, the cross sectional areas being referred to are thecross sectional areas perpendicular to the flow direction in the bypassflow channel 118. In the depicted embodiment, the shape of the first andsecond bypass taps 122, 124 is such that its width is relatively narrowwith respect to its axial length. This shape helps avoid disrupting flowin the main flow channel 112. This narrow shape also controls thehydraulic diameter of the first and second bypass taps 122, 124, whichassists in laminarizing flow through the bypass flow channel 118. Thedepicted LFE 106 is also cylindrical in shape, though, as depicted inthe exemplary embodiment in FIGS. 6 and 7, it will be appreciated thatit could be configured in various other geometric shapes, as needed ordesired.

It will be appreciated that the configurations of the first and secondbypass taps 122, 124 depicted in FIG. 5 are merely exemplary, and thatthe first and second flow element sensor taps 123, 125 may be variouslyconfigured. For example, as illustrated in the embodiment depicted inFIGS. 6 and 7, the first and second bypass taps 122, 124 may beconfigured with various polygonal geometric shapes. As will also bedescribed further below, the first and second bypass taps 122, 124 maybe configured with multiple round, rectangular, or other geometriccross-sectional shapes. Although the cross-sectional area of the firstand second bypass taps 122, 124 is not uniform compared to the LFE 106and the bypass flow channel 118, the hydraulic diameter of the first andsecond bypass taps 122, 124 is preferably equal to (or approximatelyequal to) the hydraulic diameter of the bypass flow channel 118, whichaids in reduction of non-linear pneumatic effects.

With reference now to FIGS. 9 and 10, another embodiment of the LFE 106that may be used to implement the flow sensor 100 is depicted. This LFE106 includes integrated bypass channels 902 (e.g., 902-1, 902-1). Inparticular, the bypass channels 902 are configured as recesses in theouter surface 904 of the LFE 106 that wrap around the perimeter of theLFE 106 and fluidly communicate the first and second bypass taps 122,124 with the bypass flow channel 118. With this configuration, when theLFE 106 is disposed in the main flow channel 112, it implements a pairof captured bypass channels 902 that may be relatively long, whileminimizing space. It will be appreciated that the bypass channels 902may replace all or part of the bypass flow channel 118 depicted in FIGS.1-4.

The LFE 106 depicted in FIGS. 9 and 10 is also configured to include akeying feature 906, which allows the LFE 106 to be rotated to aplurality of different rotational positions within the main flow channel112. Varying the rotational position of the LFE 106 will change theeffective length of the bypass channels 902, and thereby change thefluid flow rate through the bypass channels 902. For example, in a highflow position the length of the bypass channels 902 is relatively longto limit the bypass flowrate, which is useful for high flow rateproducts. In a low flow position, the length of the bypass channels isrelatively short, allowing more flow through the bypass flow channel118, which is useful for low flow rate product.

In one particular embodiment, when the LFE 106 is disposed within themain flow channel 112 in the high flow position, a portion of the fluidflowing through the LFE will flow, for example, out the first bypass tap122, traverse the entire length of the first bypass channel 902-1, andthen enter the bypass flow channel 118. The fluid in the bypass flowchannel 118 will then exit the bypass flow channel 118, traverse theentire length of the second bypass channel 902-2, and then through thesecond bypass tap 124, and back into the LFE 106. Conversely, when theLFE 106 is disposed within the main flow channel 112 in the low flowposition, a portion of the fluid flowing through the LFE will flow, forexample, out the first bypass tap 122, and then directly enter thebypass flow channel 118 without traversing the first bypass channel902-1. Similarly, the fluid in the bypass flow channel 118 will thenexit the bypass flow channel 118, flow through the second bypass tap124, and back into the LFE 106, without traversing the second bypasschannel 902-2.

The LFE 106 depicted in FIGS. 9 and 10 and described above is merelyexemplary of the configuration of one embodiment. It will be appreciatedthat the LFE 106 may be variously configured. For example, as depictedin FIGS. 11-14, the LFE 106 may be implemented such that one or both ofthe bypass channels 902 may be implemented in a serpentineconfiguration, thereby providing an even longer bypass flow channels902. It will be appreciated that the depicted serpentine configurationis merely exemplary of one alternate bypass channel implementation. AsFIGS. 11-14 also depict, one or both of the first and second bypass taps122, 124 may be disposed outside of the laminarizing zone of the of theLFE 106.

In addition to the variations in the disposition of the first and secondbypass taps 122, 124, and as was previously noted, the configuration ofthe first and second bypass taps 122, 124 may also be varied. Forexample, and with reference now to FIGS. 15 and 16, the first and secondbypass taps 122, 124 may each be implemented as multiple taps 122-1,122-2, 122-3, . . . 122-N, 124-1, 124-2, 124-3, . . . 124-N. The number,size, and shape of the first and second bypass taps 122, 124 may vary,but is preferably selected to maintain an approximately continuoushydraulic diameter through the first and second bypass channels 902.Although the multiple taps are depicted as being implemented with an LFE106 that has serpentine flow channels 902, it will be appreciated thatthe multiple taps could also be implemented in the LFE 106 configurationdepicted in FIGS. 5-7, 9, and 10.

Referring now to FIG. 17, a simplified cross section view of a portionof another embodiment of the flow sensor 100 is depicted. In thisembodiment, the LFE 106 is configured with a geometry that maintainssubstantially equal fluid velocities at the first and second bypass taps122, 124. As a result, the flow sensor 100 exhibits symmetrical flowsensitivity in both directions of flow 126, 128. With equal fluidvelocities at the bypass taps 122, 124, the static pressures exerted atthese taps are independent of acceleration of velocity (see Bernoulliequation). To implement this, the LFE 106 and/or main flow channel 112are configured such that there is a uniform cross-section between area1702 and 1703 between the bypass taps 122, 124 in the main flow channel112.

Those of skill in the art will appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the embodiments disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. Some ofthe embodiments and implementations are described above in terms offunctional and/or logical block components (or modules) and variousprocessing steps. However, it should be appreciated that such blockcomponents (or modules) may be realized by any number of hardware,software, and/or firmware components configured to perform the specifiedfunctions. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the present invention. For example, anembodiment of a system or a component may employ various integratedcircuit or software components, e.g., memory elements, digital signalprocessing elements, logic elements, look-up tables, mathematicalfunctions or the like, which may carry out a variety of functions underthe control of one or more microprocessors or other control devices. Inaddition, those skilled in the art will appreciate that embodimentsdescribed herein are merely exemplary implementations.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein may be implementedor performed with a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components,end-user computer or any combination thereof designed to perform thefunctions described herein. A general-purpose processor may be amicroprocessor, but in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine. Aprocessor may also be implemented as a combination of computing devices,e.g., a combination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration. The word “exemplary” is usedexclusively herein to mean “serving as an example, instance, orillustration.” Any embodiment described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otherembodiments.

In this document, relational terms such as first and second, and thelike may be used solely to distinguish one entity or action from anotherentity or action without necessarily requiring or implying any actualsuch relationship or order between such entities or actions. Numericalordinals such as “first,” “second,” “third,” etc. simply denotedifferent singles of a plurality and do not imply any order or sequenceunless specifically defined by the claim language. The sequence of thetext in any of the claims does not imply that process steps must beperformed in a temporal or logical order according to such sequenceunless it is specifically defined by the language of the claim. Theprocess steps may be interchanged in any order without departing fromthe scope of the invention as long as such an interchange does notcontradict the claim language and is not logically nonsensical.

Furthermore, depending on the context, words such as “connect” or“coupled to” used in describing a relationship between differentelements do not imply that a direct physical connection must be madebetween these elements. For example, two elements may be connected toeach other physically, electronically, logically, or in any othermanner, through one or more additional elements.

While at least one exemplary embodiment has been presented in theforegoing detailed description of the invention, it should beappreciated that a vast number of variations exist. It should also beappreciated that the exemplary embodiment or exemplary embodiments areonly examples, and are not intended to limit the scope, applicability,or configuration of the invention in any way. Rather, the foregoingdetailed description will provide those skilled in the art with aconvenient road map for implementing an exemplary embodiment of theinvention. It being understood that various changes may be made in thefunction and arrangement of elements described in an exemplaryembodiment without departing from the scope of the invention as setforth in the appended claims.

What is claimed is:
 1. A flow sensor, comprising: a main flow bodyhaving a first main flow port, a second main flow port, and a main flowchannel between the first main flow port and the second main flow port;a laminar flow element disposed within the main flow channel between thefirst main flow port and the second main flow port and having a firstend, a second end, and an outer surface, the first end facing the firstmain flow port, the second end facing the second main flow port; abypass element disposed adjacent to the main flow body and including abypass flow channel; a first bypass tap extending through the outersurface of the laminar flow element and disposed between the first endand the second end of the laminar flow element, the first bypass tapfluidly communicating the main flow channel with the bypass flowchannel; and a second bypass tap extending through the outer surface ofthe laminar flow element and disposed between the first end and thesecond end of the laminar flow element, the second bypass tap fluidlycommunicating the main flow channel with the bypass flow channel,wherein: the bypass flow channel has a cross sectional area, and thefirst bypass tap and the second bypass tap each have a cross sectionalarea that is greater than the cross sectional area of the bypass flowchannel.
 2. The flow sensor of claim 1, wherein: the main flow channelis oriented about an axis that extends between the first main flow portand the second main flow port; and the first and second bypass taps areeach configured in a direction perpendicular to the axis.
 3. The flowsensor of claim 2, wherein: the first bypass tap and the second bypasstap each have a width in a direction parallel to the axis and a lengthin a direction perpendicular to the width; and the width is less thanthe length.
 4. The flow sensor of claim 1, wherein the bypass channel,the first bypass tap, and the second bypass tap have approximately equalhydraulic diameters.
 5. The flow sensor of claim 1, further comprising:a flow sensor coupled to the bypass element and disposed within thebypass flow channel, the flow sensor configured to sense fluid flowthrough the bypass flow channel.
 6. The flow sensor of claim 1, wherein:the main flow channel is oriented about an axis that extends between thefirst main flow port and the second main flow port; and the laminar flowelement is configured with a geometry that maintains substantially equalfluid velocities along the direction of the axis at the first bypass tapand the second bypass tap.
 7. The flow sensor of claim 6, wherein thefirst and second bypass taps are configured perpendicular to the axis.8. A flow sensor, comprising: a main flow body having a first main flowport, a second main flow port, a main flow channel between the firstmain flow port and the second main flow port, a first bypass tap, asecond bypass tap, and a bypass flow channel; a laminar flow elementdisposed within the main flow channel between the first main flow portand the second main flow port and having a first end and a second end,the first end facing the first main flow port, the second end facing thesecond main flow port; and a flow sensor coupled to the main flow bodyand disposed within the bypass flow channel, the flow sensor configuredto sense fluid flow through the bypass flow channel; wherein: the firstbypass tap is disposed between the first end and the second end of thelaminar flow element, and fluidly communicates the main flow channelwith the bypass flow channel, the second bypass is tap disposed betweenthe first end and the second end of the laminar flow element, andfluidly communicates the main flow channel with the bypass flow channel,the bypass flow channel has a cross sectional area, and the first bypasstap and the second bypass tap each have a cross sectional area that isgreater than the cross sectional area of the bypass flow channel.
 9. Theflow sensor of claim 8, wherein the bypass flow channel, the first flowelement sensor tap, and the second flow element sensor tap haveapproximately equal hydraulic diameters.
 10. The flow sensor of claim 8,wherein: the main flow channel is oriented about an axis that extendsbetween the first main flow port and the second main flow port; and thefirst and second bypass taps are each configured in a directionperpendicular to the axis; the first bypass tap and the second bypasstap each have a width and in a direction parallel to the axis and alength in a direction perpendicular to the width; and the width is lessthan the length.
 11. The flow sensor of claim 8, wherein: the main flowchannel is oriented about an axis that extends between the first mainflow port and the second main flow port; and the laminar flow element isconfigured with a geometry that maintains substantially equal fluidvelocities along the direction of the axis at the first bypass tap andthe second bypass tap.
 12. The flow sensor of claim 11, wherein thefirst and second bypass taps are configured perpendicular to the axis.13. A flow sensor, comprising: a main flow body having a first main flowport, a second main flow port, a main flow channel between the firstmain flow port and the second main flow port, a first bypass tap, and asecond bypass tap; a laminar flow element disposed within the main flowchannel between the first main flow port and the second main flow portand having a first end, a second end, and an outer surface, the firstend facing the first main flow port, the second end facing the secondmain flow port; and a bypass element disposed adjacent to the main flowbody and having a bypass flow channel, wherein: the first bypass tap isdisposed between the first end and the second end of the laminar flowelement, and fluidly communicates the main flow channel with the bypassflow channel, the second bypass tap is disposed between the first endand the second end of the laminar flow element, and fluidly communicatesthe main flow channel with the bypass flow channel, the main flowchannel is oriented about an axis that extends between the first mainflow port and the second main flow port, the first bypass tap and thesecond bypass tap each have a width and in a direction parallel to theaxis and a length in a direction perpendicular to the width, the widthis less than the length, and the first bypass tap and the second bypasstap each have a cross sectional area that is greater than the crosssectional area of the bypass flow channel.
 14. The flow sensor of claim13, wherein, the first and second bypass taps are each configured in adirection perpendicular to the axis.
 15. The flow sensor of claim 13,wherein: the laminar flow element is configured with a geometry thatmaintains substantially equal fluid velocities along the direction ofthe axis at the first bypass tap and the second bypass tap.